Method and Apparatus for Catching and Retrieving Objects in a Well

ABSTRACT

A magnet assembly can be attached to, or placed in the vicinity of, a conventional bell nipple to generate a magnetic field within the central bore of the bell nipple. The magnetic field catches falling metal objects and prevents such objects from passing beyond the bell nipple and entering the subterranean portions of a wellbore. An optional diverter assembly slows the velocity of falling metal objects before reaching the magnet assembly, while also wiping the outer surface of pipe or other items lowered into a wellbore.

CROSS REFERENCES TO RELATED APPLICATION

PRIORITY OF U.S. PROVISIONAL PATENT APPLICATION SER. NO. 61/510,229,FILED Jul. 21, 2011, AND U.S. PROVISIONAL PATENT APPLICATION SER. NO.61/610,757, FILED Mar. 14, 2012, BOTH INCORPORATED HEREIN BY REFERENCE,IS HEREBY CLAIMED.

STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLYSPONSORED RESEARCH AND DEVELOPMENT

NONE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a method and apparatus for preventingunwanted objects from entering subterranean portions of a wellbore. Moreparticularly, the present invention pertains to the use of magneticfield(s) to catch falling objects within a wellbore. More particularlystill, the present invention pertains to an apparatus for generatingmagnetic field(s) between a rig floor of a drilling or completion rigand a wellhead, such as in or near a bell nipple assembly, in order toprevent unwanted objects from falling into a wellbore below saidwellhead.

2. Brief Description of the Prior Art

A bell nipple is a large diameter length of pipe utilized on mostdrilling and completion rigs. In most cases, a bell nipple is installedat or near the top of a rig's blowout preventers and extends to the wellopening at the rig floor; the bell nipple typically serves as a “funnel”to guide drilling tools into and out of the upper opening of a well.Most conventional bell nipples also serve as conduits for drilling mudsand/or other fluids present within a well. As such, most conventionalbell nipples are typically configured with a side outlet to permit fluidto flow from a well to a rig's surface fluid treating equipment such asshale shakers and mud tanks.

Unfortunately, not all objects that a bell nipple guides into a wellboreare beneficial. Objects can sometimes accidentally fall into a wellborefrom the rig floor. In other instances, objects can be purposely thrownor dropped into a well as an intentional act of sabotage. If suchobjects are not stopped before entering the subterranean portion of thewellbore, the objects can prevent downhole equipment from functioningproperly and can often impede the drilling and completion process.

Relatively large objects can generally be retrieved from a wellboreusing specially designed “fishing tools.” Such fishing tools are loweredinto a wellbore and connect to a dropped object within the wellbore.Thereafter, the fishing tools and the connected object can both besafely retrieved from the wellbore. In many instances, the retrievalprocess for such large objects can be relatively simple because the sizeof the objects enables such objects to be grasped and lifted out of thewellbore.

By contrast, relatively small objects dropped in a wellbore andparticularly metal objects—can often cause the most disruption todownhole equipment and related operations. For example, duringcompletion operations, small pieces of metal present in a wellbore canprevent packers and other completion tools from sealing against a casingwall. During open hole drilling operations, such small metal objects candestroy very expensive downhole equipment such as PolycrystallineDiamond Compact (PDC) bits.

Such small objects can also be very difficult to retrieve from awellbore, as they are often too small to be grasped using conventionalfishing tools. This is especially true for small metal objects, andparticularly small metal objects that have an irregular shape or smallpieces that can be broken up during the retrieval process.Unfortunately, many drilling rigs typically have many small metalobjects (such as, for example, wrenches, chain, bolts, tong dies andnuts) at or near the rig floor. Such objects, which are in relativelyclose proximity to the upper opening of a well, are at risk of fallinginto a wellbore.

As noted above, such relatively small metal objects can causesignificant disruptions to downhole operations. Further, fishingoperations for small metal objects can be very time consuming and, as aresult, very costly. Accordingly, the best way to prevent suchdisruptions and to avoid long and expensive fishing operations for suchsmall objects is to keep such objects from entering a wellbore in thefirst place.

Rig operating procedures frequently dictate that when no pipe is presentin a wellbore that the blind rams in the blow out preventer (“BOP”)assembly be closed in order to block access to the wellbore and keep anyunwanted falling objects from entering the wellbore from above the BOPassembly. If an object is dropped into the well at the rig floor, withthe blind rams closed, the object will not fall all the way into thesubterranean portion of a wellbore; however, this solution is less thanoptimal, because object must still be retrieved from the top of the ramsbefore operations can resume. Such retrieval process typically requiresdraining the BOP assembly to locate the object, opening the bonnet inthe BOP assembly, finding and retrieving the object, and closing andretesting the BOP assembly to the required test pressures. Thisretrieval process—while frequently quicker and less expensive thanfishing the item from the bottom of the well—is nonetheless expensiveand time consuming and costly.

Thus, there is a need for an apparatus and method for catching droppedobjects, and particularly metallic objects, before such objects enterthe subterranean portion of a well. Such apparatus and method shouldprevent dropped objects from falling further into a wellbore, and shouldhold such objects for ultimate retrieval and removal from a wellbore.Such apparatus can be disposed at virtually any location(s) between arig floor of a drilling or completion rig, and a wellhead assembly of awell. In many cases, said apparatus can be situated at or in proximitywith a bell nipple assembly.

SUMMARY OF THE PRESENT INVENTION

The present invention comprises an apparatus for generating a magneticfield that can be attached to, or placed in the vicinity of, or made anintegral part of a conventional bell nipple. The magnetic field is usedto catch falling metal objects from passing beyond the bell nipple andentering the subterranean portions of a wellbore.

In the preferred embodiment, the apparatus of the present inventioncomprises the following primary components, or combinations thereof,that cooperatively work together to catch falling metallic objects in awellbore, thereby saving rig time and enhancing overall safety:

Magnet Assembly:

A magnet assembly of the present invention comprises at least one magnetand is disposed on, around, or as an integral part of the bell nipple.The magnet(s) of the magnet assembly of the present invention can besized based on the internal diameter of a bell nipple, as well as theability to catch certain representative objects that have been droppedinto or fished out of wellbores in the past.

In the preferred embodiment, the magnet assembly of the presentinvention can be mounted at or near the bell nipple using a movableassembly, such that said magnets can be selectively moved or positionedaway from the bell nipple to prevent magnetic interference with loggingtools or other equipment that may be sensitive to magnetic fields.

Divert (Finger) Assembly:

A diverter assembly can be mounted above the magnet assembly, and canact as a barrier to slow the velocity of a falling object passingthrough a bell nipple. Although said diverter assembly may only “break”the fall of an object, even a momentary reduction of velocity cangreatly improve the ability of the magnet assembly to catch largerand/or heavier objects.

As a secondary function (in addition to slowing the velocity of fallingobjects), the diverter assembly of the present invention also acts as awiper to clean the outer surface of pipe or other equipment passingthrough the bell nipple. Frequently, multiple different pipe sizes areused in the same drill string, which is a practice known as a tapereddrill string. Several diverter assemblies of the present invention canbe stacked to match each of the different pipe sizes that are being usedin a tapered string. Use of such multiple diverter assemblies eliminatesthe need to work over an open wellbore to change out conventional pipewipers, thereby resulting in time savings and a decrease in the chancethat objects will be inadvertently dropped into a wellbore.

Gate Assembly:

A full closing gate that can extend across the central bore of the bellnipple (that is, the path into the well) is beneficially positionedunder a magnet apparatus. The gate serves as a secondary closure of thewell bore when the rig has pipe out of the hole.

The full-closing gate assembly of the present invention, which can beselectively operated by a driller or other automated system, can beclosed when pipe is not in the well in order to stop falling objects.Said gate assembly of the present invention saves time and expenseassociated with actuating the BOP assembly and, further, eliminates theneed for such unnecessary actuation.

Dimensions set forth herein and in the attached drawings areillustrative only and are not intended to be, and should not beconstrued as, limiting in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiments, is better understood when read in conjunctionwith the appended drawings. For the purpose of illustrating theinvention, the drawings show certain preferred embodiments. It isunderstood, however, that the invention is not limited to the specificmethods and devices disclosed. Further, dimensions, materials and partnames are provided for illustration purposes only and not limitation.

FIG. 1 depicts a side perspective view of a magnet sleeve assembly ofthe present invention in a closed position.

FIG. 2 depicts a side perspective view of a magnet sleeve assembly ofthe present invention of the present invention in an open position.

FIG. 3 depicts a side sectional view of a conventional bell nippleassembly and related equipment installed on a drilling rig.

FIG. 4 depicts a side sectional view of a bell nipple assembly equippedwith a magnet sleeve assembly of the present invention.

FIG. 5 depicts a side sectional view of a bell nipple assembly equippedwith a magnet sleeve assembly and diverter assembly of the presentinvention.

FIG. 6 depicts a side sectional view of a bell nipple assembly equippedwith an alternative embodiment magnet sleeve assembly and diverterassembly of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring to the drawings, FIG. 1 depicts a side perspective view of amagnet sleeve assembly 10 of the present invention in a closed position.Generally, said magnet sleeve assembly 10 of the present invention isinstalled in close proximity to the upper opening of a wellbore (suchas, for example, near a bell nipple assembly). Said magnet sleeveassembly 10 generates a magnetic field that is beneficially directedtoward the wellbore to catch falling metal objects and prevent suchobjects from entering the subterranean portions of said wellbore.

Still referring to FIG. 1, magnet sleeve assembly 10 comprises firstsemi-cylindrical member 11 and second semi-cylindrical member 12 joinedby at least one hinge assembly comprising hinge body members 13 andhinge pin 14. When said first and second semi-cylindrical members arejoined together as depicted in FIG. 1, magnet sleeve assembly 10 has asubstantially cylindrical shape. In the preferred embodiment depicted inFIG. 1, magnet sleeve assembly 10 further comprises opposing connectionplate members 15 and 16. Fasteners such as threaded bolts 17 can bedisposed through aligned holes in said opposing connection members 15and 16 to secure first semi-cylindrical member 11 and secondsemi-cylindrical member 12 together. Optional handles 19 can be providedon the sides of magnet sleeve assembly 10.

Still referring to FIG. 1, magnets 20 are disposed on first and secondmembers 11 and 12. In the preferred embodiment of the present invention,said magnets 20 comprise are typically rare earth or ceramic magnetsexhibiting desired magnetic characteristics (that is, creates their ownpersistent magnetic field).

FIG. 2 depicts a side perspective view of magnet sleeve assembly 10 ofthe present invention in a substantially open position. As noted above,magnet sleeve assembly 10 comprises first semi-cylindrical member 11 andsecond semi-cylindrical member 12 moveably joined by hinges having hingebody members 13 and hinge pins 14. Opposing connection members 15 and 16have aligned holes 18 for receiving bolts 17 which, in turn, are used tosecure first semi-cylindrical member 11 and second semi-cylindricalmember 12 together. As depicted in FIG. 2, optional handles/lifting eyes19 are provided on the sides of magnet sleeve assembly 10.

FIG. 3 depicts a side sectional view of a conventional bell nippleassembly 120 and related equipment installed on a drilling rig. Bellnipple assembly 120 comprises a length of pipe 123 having a centralthrough-bore 124, as well as a side outlet port 121 and outlet line 122.As depicted in FIG. 3, bell nipple assembly 120 is connected at itsupper end to rotary assembly 130, and at its lower end to blow-outpreventer (“BOP”) assembly 110. Rotary assembly 130 is mounted at rigfloor 140 having upper surface 141, and defining an upper opening 131.BOP assembly 110 is connected to wellhead 100 which is mounted to theupper portion of a wellbore (not shown in FIG. 3) extending into theearth's crust. BOP assembly 110 generally comprises ram assembly 111 andannular preventer assembly 112.

Bell nipple assembly 120 acts as a “funnel” to guide drilling tools intoand out of the upper opening of a wellbore. Unfortunately, not allobjects that a bell nipple guides into a wellbore are beneficial, suchas chain segment 150 that is depicted falling in central through-bore124 of bell nipple assembly 120. If falling objects such as chainsegment 150 are not stopped before entering the subterranean portion ofa wellbore, such objects can prevent downhole equipment from functioningproperly and can often negatively impede the drilling process asdetailed herein.

FIG. 4 depicts a side sectional view of the same basic well componentsas depicted in FIG. 3, except that magnet sleeve assembly 10 isinstalled on central body member 123 of bell nipple assembly 120.Additionally, optional gate valve assembly 30 is installed between bellnipple assembly 120 and BOP assembly 110. In the preferred embodiment,magnet sleeve assembly 10 of the present invention can be sized based onthe dimensions of bell nipple assembly 120.

Although magnet sleeve assembly 10 is depicted in FIG. 4 as beingsecured in a fixed or stationary position, it is to be observed thatmagnet sleeve assembly 10 of the present invention can be mounted at ornear bell nipple assembly 120 using an assembly that selectively movesthe magnets of said magnet sleeve assembly 10 away from said bell nippleassembly when desired. For example, it may be beneficial to selectivelymove said magnets away from bell nipple assembly 120 to prevent magneticinterference with logging tools or other equipment that may be sensitiveto magnetic fields, or when circulating large concentrations of metallicdebris in a rig mud system (such as, for example, when milling up stuckmetal objects in a well). Such assembly for repositioning said magnetscan be manually operated, or remotely actuated using pneumatic orhydraulic power.

Still referring to FIG. 4, gate assembly 30 can be closed to extendsubstantially across central through-bore 124 of bell nipple assembly120. Said gate assembly 30 permits a secondary means for quickly closingaccess to the upper surface of the well bore when pipe is out of thewell. Although said gate assembly 30 can be manually operated, in thepreferred embodiment it is remotely actuated using pneumatic orhydraulic power.

Said gate assembly 30 of the present invention can be actuated when pipeis not in the well as an additional means to prevent falling objectsfrom entering subterranean portions of a wellbore, especially when metalobjects have fallen into said wellbore (and must be retrieved), or whenthe present invention must be removed or checked. Said gate assembly 30of the present invention saves time and expense associated withactuating the BOP assembly 110 just to “catch” falling objects and,further, eliminates the need for such unnecessary actuation whichcreates undesirable wear and tear on said BOP assembly 110. The primaryfunction of BOP assembly 110 is to hold back fluid pressure from below,often in an emergency or unexpected situation. Because such unnecessaryactuation of said BOP assembly 110 can negatively affect subsequentfunctionality and reliability of said BOP assembly 110, the inclusion ofgate assembly 30 (particularly in conjunction with the other componentsof the present invention) provides a significant added element of safetyto rig operations.

As depicted in FIG. 4, magnet sleeve assembly 10 of the presentinvention, and more particularly magnets 20 thereof, create magneticfield 21. In the preferred embodiment, said magnetic field is generallyfocused or directed toward central through-bore 124 of bell nippleassembly 120. As a result, metal objects dropped into the upper opening131 of a well, such as chain segments 150, are caught in said magneticfield 21; accordingly, such metal objects do not pass bell nippleassembly 120, and do not enter the subterranean portions of a well bore.Such objects (such as, for example, chain segments 150) can be easilyretrieved from bell nipple assembly 120.

FIG. 5 depicts a side sectional view of a bell nipple assembly 120equipped with magnet sleeve assembly 10, as well as optional diverterassembly 40 and optional gate assembly 30 of the present invention. Inthe preferred embodiment, diverter assembly 40 is mounted above 10magnet assembly, and has a plurality of substantially flexible fingers41 that extend into central through-bore 124 of bell nipple assembly120. Said fingers 41 act as an impediment to slow the velocity of afalling objects passing through central through-bore 124 of bell nippleassembly 120. Although said diverter assembly 40 may only “break” thefall of an object, even a momentary reduction of velocity can greatlyimprove the ability of magnet assembly 10 to catch larger and/or heavierobjects.

As a secondary function (in addition to slowing the velocity of fallingobjects), diverter assembly 40 of the present invention also acts as awiper to clean the external surfaces of pipe or other equipment passingthrough bell nipple assembly 120. Frequently, multiple different sizesof pipe are used in the same drill string, which is a practice known asa tapered drill string. If desired, multiple diverter assemblies 40 ofthe present invention can be stacked to match each of the different pipesizes that are being used in a tapered string. Use of such multiplediverter assemblies eliminates the need to work over an open wellbore tochange out conventional pipe wipers, thereby resulting in time savingsand a decrease in the chance that objects will be inadvertently droppedinto a wellbore. FIG. 6 depicts a side sectional view of a bell nippleassembly equipped with an alternative embodiment magnet sleeve assemblyand diverter assembly of the present invention.

Said magnet assembly can be beneficially positioned proximate to a bellnipple, and situated above or below the side outlet of said bell nipple.For example, FIG. 5 depicts magnet assembly 10, diverter assembly 40 andgate assembly 30 mounted above side outlet port 121 of bell nippleassembly 120. Because any liquid in central through-bore 124 of bellnipple assembly 120 drains through said side outlet port 121, the liquidlevel within said through-bore 124 does not extend above said outletport 121. Accordingly, magnetic field 21 generated by the magnetassembly 10 extends into a “dry” portion of bell nipple assembly 120(that is, the portion of central through-bore 124 of bell nippleassembly 120 that does not contain drilling mud or other liquid).

Conversely, as depicted in FIG. 6, magnet sleeve assembly 10 can beinstalled proximate to bell nipple assembly 120, and positioned belowsaid outlet port 121 of bell nipple assembly 120. In such aninstallation, magnetic field 21 generated by magnet assembly 10 extendsinto a “wet” portion of bell nipple assembly 120 (that is, a portion ofbell nipple central through-bore 124 that contains drilling mud or otherliquid).

In the event that an object has fallen or been dropped into a well, anypipe or other equipment can first be retrieved from said well.Thereafter, for installations equipped with gate assembly 30, said gateassembly 30 can be shifted to a closed position. Thereafter, bell nipple120 can be removed, or the internal surfaces of said bell nippleassembly 120 can otherwise be accessed, in order to retrieve the droppedor fallen object. With gate assembly 30 in a closed position, any objectthat may fall out of magnetic field 21 will be stopped at said gateassembly 30 (thereby permitting fast and easy retrieval), and will notfall into BOP assembly 110 or subterranean portions of a well situatedtherebelow. As noted above, said gate assembly 30 saves time and expenseby eliminating the need for actuating BOP assembly 110 simply to blockentry into subterranean portions of a wellbore.

It is to be observed that the magnet assembly of the present inventioncan be disposed at virtually any position along the distance that existsbetween: (1) a rig floor of a drilling or completion rig; and (2) awellhead of a well being serviced by said drilling or completion rig.For example, it is possible that said magnet assembly of the presentinvention and related method could be incorporated directly within a BOPassembly or wellhead assembly. However, without limiting the scope ofthe present invention in any manner, the simplest and most effectivemanner of implementing the present invention will frequently involvepositioning the magnet assembly of the present invention proximate to abell nipple assembly as described herein.

The above-described invention has a number of particular features thatshould preferably be employed in combination, although each is usefulseparately without departure from the scope of the invention. While thepreferred embodiment of the present invention is shown and describedherein, it will be understood that the invention may be embodiedotherwise than herein specifically illustrated or described, and thatcertain changes in form and arrangement of parts and the specific mannerof practicing the invention may be made within the underlying idea orprinciples of the invention.

1. A magnet assembly comprising at least one magnet proximate to a bellnipple assembly having an upper end, a lower end and a central bore,wherein said at least one magnet generates a magnetic field directedtoward said central bore.
 2. The magnet assembly of claim 1, furthercomprising a gate assembly disposed below said at least one magnet. 3.The magnet assembly of claim 1 further comprising a diverter assemblydisposed above said at least one magnet, wherein said diverter assemblycomprises at least one flexible member extending into said central boreof said bell nipple assembly.
 4. The magnet assembly of claim 1, whereinsaid at least one magnet comprises a rare earth material.
 5. The magnetassembly of claim 1, wherein said at least one magnet comprises aceramic material.
 6. The magnet assembly of claim 1, further comprising:a. a first body member having at least one magnet attached thereto; b. asecond body member having at least one magnet attached thereto, saidsecond body member hingeably attached to said first body member.
 7. Themagnet assembly of claim 6, further comprising an automated assembly foropening and closing said first and second body members.
 8. A method forcatching objects falling in a well comprising the step of placing atleast one magnet proximate to a bell nipple assembly having a centralbore, wherein said at least one magnet generates a magnetic fielddirected at said central bore of said bell nipple assembly.
 9. Themethod of claim 8, further comprising a gate valve assembly disposedbelow said at least one magnet.
 10. The method of claim 8, furthercomprising a diverter assembly disposed above said at least one magnet.11. The method of claim 10, wherein said diverter assembly comprises atleast one flexible member extending into said central bore of said bellnipple assembly.
 12. A method for catching objects falling in a boreextending between a rig floor of a rig and a wellhead of a well,comprising the step of generating a magnetic field directed at saidbore.
 13. The method of claim 12, wherein said magnetic field isgenerated by at least one magnet disposed between said rig floor andsaid wellhead.
 14. The method of claim 13, further comprising a gatevalve assembly disposed below said at least one magnet.
 15. The methodof claim 13, further comprising a diverter assembly disposed above saidat least one magnet.
 16. The method of claim 15, wherein said diverterassembly comprises at least one flexible member extending into saidbore.